In recent years, robots for use in mounting electronic components or the like are required to have a longer stroke together with high speed and high accuracy.
Conventionally, as a robot for executing a variety of operations with high positional accuracy on a workpiece such as a board, there is the robot shown in FIG. 11 and FIG. 12.
This is provided with an X-axis table 52 supported in a cantilever style on an Y-axis table 51. The X-axis table 52 can be positioned in an arbitrary position in the Y-direction. The X-axis table 52 is mounted with a working head section 53 that can be positioned in an arbitrary position in the X-direction. The working head section 53 is mounted with a position recognition means 54 for recognizing the position of a workpiece W and a working member 55 such as a component suction nozzle, which are spaced apart at a specified distance D in the X-direction as shown in FIG. 12.
This robot recognizes with high accuracy the working position of the working head section 53 by means of the position recognition means 54 by moving the working head section 53 into the working position of the workpiece W by means of the Y-axis table 51 and the X-axis table 52, and moves the working head section 53 by means of the Y-axis table 51 or the X-axis table 52 on the basis of the recognized working position and the above-mentioned distance D, thereby guiding the working member 55 into the working position for the execution of the operation.
The X-axis table 52 is supported in a cantilever style on the Y-axis table 51, and this causes an issue that vibration tends to occur when the X-axis table 52 is made to have a long stroke in correspondence to the workpiece W and an issue that it takes a period of time to position the working head section 53 when stopping a high-speed operation. A bolt for fastening the Y-axis table 51 to the X-axis table 52 tends to become loose. There is a further issue that the positioning accuracy of the working head section 53 is significantly reduced by the yawing and rolling of the Y-axis table 51.
A rectangular coordinate type robot (Japanese Laid-Open Patent Publication No. 3-221385) that we have already proposed in order to solve the above-mentioned issues has a construction as shown in FIG. 13 and FIG. 14.
A pair of Y-axis tables 1 and 2 are arranged parallel to each other, and the Y-axis tables 1 and 2 are provided with first moving units 4 and S that move while being guided along the Y-axis tables 1 and 2, respectively.
Between the Y-axis tables 1 and 2 is provided an X-axis table 3 perpendicular to the Y-axis tables 1 and 2. The X-axis table 3 is provided with a second moving unit 21 that is guided along the X-axis table 3.
One end portion of the X-axis table 3 and the first moving unit 4 located on the side of the one Y-axis table 1 are engaged with each other while being pivotal around the axes that are perpendicular to the Y-axis and X-axis tables. The other end portion of the X-axis table 3 and the first moving unit 5 located on the side of the other Y-axis table 2 are engaged and supported with each other while being pivotal around the axes that are perpendicular to the Y-axis and X-axis tables and slidable in the axial direction of the X-axis table 3.
The second moving unit 21 is provided with a workpiece position recognition means 25 and a working member 26.
In more detail, the Y-axis tables 1 and 2 are internally provided with threaded shafts (implemented by, for example, ball screws) 6 and 7 and motors 8 and 9 for rotating these threaded shafts 6 and 7. The first moving units 4 and 5 are meshed with the respective threaded shafts 6 and 7 via nuts (not shown).
The X-axis table 3 is supported and engaged pivotally with the first moving units 4 and 5 located on the Y-axis tables 1 and 2 and slidably in the axial direction of the X-axis table 3.
That is, the first moving units 4 and 5 located on the Y-axis tables 1 and 2 have their center portions provided with engagement shafts 11 and 12 that are protruding in the vertical direction (in the direction perpendicular to both the Y-axis table and the X-axis table) as shown in FIG. 15.
To one end portion of the X-axis table 3 is fixed a connecting member 14 that is pivotally engaged with the engagement shaft 11 of the first moving unit 4 via a bearing 13. To the other end portion of the X-axis table 3 are fixed fixing sections 15a of a slide block 15 as shown in FIG. 16, and a movable section 15b that is made slidable between the fixing sections 15a of the slide block 15 and is pivotally engaged with the engagement shaft 12 of the first moving unit 5 via a bearing 16.
Therefore, by driving the motors 8 and 9 in synchronism, the X-axis table 3 can be moved into an arbitrary position along the Y-axis tables 1 and 2 via the first moving units 4 and 5.
The second moving unit 21 provided on the X-axis table 3 is provided with a threaded shaft (implemented by, for example, a ball screw) 22 and a motor 23 for rotating this threaded shaft 22 arranged inside the X-axis table 3 as shown in FIG. 13, and the second moving unit 21 is meshed with the threaded shaft 22 via a nut 24.
The second moving unit 21 has its one side surface provided with a working member mounting plate 27 that is movable in the axial direction of the X-axis table 3. The second moving unit 21 is provided with a threaded shaft (implemented by, for example, a ball screw) 29 and a motor 30 for rotating this threaded shaft 29, while a nut 28 attached to the back surface of the working member mounting plate 27 is meshed with the threaded shaft 29.
The working member mounting plate 27 is mounted with the workpiece position recognition means (e.g., a camera) 25 and a workpiece working tool, which is an example of the working member 26. The reference numerals 31 and 32 denote cable units for transmitting a power signal and a control signal.
However, the rectangular coordinate type robot shown in FIG. 13 through FIG. 16 has the disadvantages of a deterioration in accuracy due to the looseness of the rotating portions occurring when performing the positioning in the Y-axis direction of a Y.sub.1 -axis and a Y.sub.2 -axis as well as the disadvantage that it takes a period of time to settle the positioning.
It has also been unable to provide a sufficient added weight of the rotational and slide mechanisms for the issue in terms of space.
Furthermore, in regard to the positioning accuracy, the component size has been reduced and component lead pitch has been reduced (0.3-mm pitch) in recent years, and accordingly, a mounting accuracy of .+-.25 .mu.m is required. However, there has been a vibration of the maximum amplitude of about 30 .mu.m in the positioning stage according to the conventional system, and a settling time (time to the achievement of settlement within a range of .+-.5 .mu.m) of about 400 msec has currently been required.
The present invention has the object of providing a rectangular coordinate type robot capable of executing a positioning operation without reducing the rigidity when moving an X-axis table in a Y-axis direction of a Y.sub.1 -axis and a Y.sub.2 -axis.